Iron-type golf club head with sole having stable static address position

ABSTRACT

An iron-type golf club head having a sole, a center of gravity CG, and a static contact point SCP on the sole substantially vertically below the CG for providing stability when the club head is in an address position, but the sole has no points lower than the SCP when the club head is in the address position. Additionally, the club head may have a centerline plane orthogonal to the plane of the club face and containing the centerline of the club face, with the center of gravity lying in the centerline plane and the lowest point LP on the sole also lying substantially in the centerline plane when the centerline plane is substantially vertical, for minimizing mis-hits with the club head.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This U.S. utility patent application claims the benefit of U.S.provisional patent application Serial No. 60/437,047, filed Dec. 31,2002, the entire disclosure of which is incorporated by referenceherein.

BACKGROUND

[0002] The present invention relates to the design of golf clubs, andmore particularly to designs to provide golf club heads of iron-typegolf clubs improved static stability when oriented in the addressposition.

[0003] The address position of a golf club usually refers to theorientation of the head of a golf club when a player is holding the gripand shaft of the club in a substantially vertical plane with the clubhead, attached to that shaft, being located just behind a golf ballbefore hitting same, i.e., “addressing the ball,” resting on the groundjust behind the golf ball. The sole of a golf club head is the bottomsurface(s) thereof, which may rest on the ground when the club head isin an address position.

[0004] As discussed later herein, the sole portion of an iron-type golfclub often increases in total width (as measured in the clubface-to-back direction) at locations progressing from the heel portionto the toe portion of the sole of the club head. The sole of aniron-type golf club head may be substantially flat, or may be curvedfrom heel to toe (the so-called “radius” of the sole of a club head)and/or curved from leading edge to trailing edge of the sole (theso-called “camber” of the sole of a club head), such curves causing thesole to bulge downwardly in a convex manner.

[0005] The “radius” of the sole of an iron type golf club is preferablysymmetrical with respect to the centerline plane of the club head (whichplane is discussed later herein). For example, the earlier Hogan Radiusirons, and Cleveland 792 VAS irons, are examples of club heads havingconvex “radius” and “camber” sole curvatures. Additionally, sand wedgesoften exhibit such sole curvatures.

[0006] Iron-type golf club heads are ideally designed to strike a ballwith the face centerline, as shown in FIG. 1, in a centerline planeperpendicular to both the hitting face of the club head, and the ground.However, it is well known to those skilled in the art that during a golfswing the shaft of a golf club bows outwardly away from the body of theplayer swinging the club, causing the toe of the club head to droopslightly. To compensate for such toe droop at impact with the ball, thelie angle of a club head with a given shaft should be chosen so that atimpact with the ball the centerline plane is perpendicular to both thehitting face and the ground, as shown in FIG. 1. This lie angle of aclub is said to be “dynamically-proper.” The “lie angle” of a club headis usually said to be the angle, in a vertical plane, between the axisof the hosel portion of the club head and a horizontal plane, measuredwhen the club head is oriented with its centerline plane in a verticalposition.

[0007] Herein the “address position” means a position wherein the toe ofa club head will be slightly raised, that is pivoted upwardly about theheel, as schematically shown somewhat exaggerated in FIG. 2. In otherwords, in the address position the contact point of the club head withthe ground, called the “static contact point” SCP will be slightlyheel-biased (located somewhat toward the heel) from the aforementionedcenterline plane. This is in part due to the chosen “dynamically-proper”lie angle.

[0008] Many golf clubs, especially iron-type clubs, also exhibit soleinversion or “bounce” to prevent the clubs from undesired digging intothe turf while hitting a golf ball. In a conventional golf club thebounce angle of a club head in ball striking position is the anglebetween a line (in the centerline plane, for example) from the leadingedge of the club face rearwardly toward the low point of the sole of theclub head and a horizontal line (in the same plane), is generallybetween zero and twenty degrees, and uniform along the entire length ofthe sole. A “bounce line” is defined by the lowest points of the clubhead in a plurality of planes perpendicular to the club face. This lineis also the lowest line in the face profile view of the club head. Whenin the address position, a conventional club head is staticallyunstable, as shown in FIG. 3, because the uniform bounce angle of thesole causes the aforementioned heel-biased static contact point SCP ofthe club head with the ground to be laterally (in the face-to-backdirection) offset a distance D with respect to a vertical line throughthe center of gravity CG of the club head (i.e., at address the groundcontact point of a conventional golf club head is not vertically belowthe center of gravity of the club head, but is on a line vertically tothe rear (or front) thereof, as viewed from the heel looking toward thetoe of the club head). Due to this instability, the face of aconventional club head tends to open or close at address, depending onwhether the static ground contact point is on a vertical line forward orrearward of the center of gravity, as indicated in FIG. 3. A golf clubhaving a propensity to open or close at address does not feel balancedto the player, thus undermining the player's confidence in the club.When a club is in the address position, players expect it to feelsteady, even when applying only minimal grip pressure, and they alsoexpect the club head to look square to the desired initial line of ballflight.

[0009] Those skilled in the art will appreciate that when hitting a golfball, a golf club should make initial dynamic contact with the ground ata low point LP on the sole, that lies substantially in the centerlineplane as discussed with respect to FIG. 1. This is the low point of theusually symmetrical sole radius. If the club head is not so designed,the accuracy of shots therewith may suffer. For example, initial dynamiccontact of the sole with the ground toward the toe causes the club faceto open, thereby producing an undesired fade or slice shot. Similarly,initial dynamic contact of the sole with the ground toward the heelcauses the club face to close, producing an undesired draw or hook shot.As shown in FIG. 4, even if the lie angle of a conventional golf club is“dynamically proper,” the initial dynamic contact point of the sole withthe ground is typically still somewhat undesirably toward the toebecause the bounce angle is constant along the entire length of the soleand the width of the sole increases from heel to toe. FIG. 4 shows thatthe amount of sole surface exposed in a face view of an iron-type clubhead is greater near the toe portion of the sole (Distance B) than nearthe heel portion of the sole of the club head (Distance A). Thus, on thedownswing, the sole of a conventional club typically will initiallycontact the ground at a point along the bounce line somewhat toward thetoe as indicated in FIG. 5, causing the club face to open and anundesired fade or slice shot to result.

[0010] The ground contact lowest point LP is located slightly toward thetoe a distance from the centerline plane of from about 0.050 inches toabout 0.250 inches among clubs of a set of irons. To eliminate suchdifferences, the lie angle of the club head may be adjusted by about 0.5to about 1.5 degrees. This slight adjustment in lie angle will cause thecenterline plane to be slightly out of perpendicular to a horizontalground plane, which can result in off-center ball strikes. However, thepresent invention provides a solution to these problems.

BRIEF SUMMARY OF THE INVENTION

[0011] Hence, a need exists for an iron-type golf club that is stableand feels steady at address, thus increasing the player's confidence inthat club. It is also desirable to provide a golf club having a clubhead which will make initial dynamic contact with the ground at thecenterline plane junction with the sole, and preferably vertically belowthe center of gravity of the club head, thereby minimizing thepossibility of club head-induced hook or slice shots. The centerlineplane can be maintained perpendicular to the ground plane by modifyingsole width, radius, camber and bounce. Before such dynamic ball strikingand ground contact, steady address is achieved in the golf club head ofthe present invention by providing in the sole of the club head a staticcontact point, line and area preferably vertically below the center ofgravity of the club head when in an address position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other advantages and further features of the advantageous golfclub head of the present invention are shown in and described inconjunction with the following drawings:

[0013]FIG. 1 is a partially schematic face view of an iron-type golfclub head additionally illustrating certain aspects of the presentinvention;

[0014]FIG. 2 is a schematic view of an iron-type golf club headadditionally schematically illustrating a status contact point when theclub head is at address position;

[0015]FIG. 3 is a partially schematic heel view of an iron-type golfclub head additionally illustrating certain aspects of the presentinvention;

[0016]FIG. 4 is another face view like FIG. 1 but illustrating furtheraspects of the present invention;

[0017]FIG. 5 is a partially schematic sole view of an iron-type golfclub head additionally illustrating still further aspects of the presentinvention;

[0018]FIG. 6 is another sole view like FIG. 5, but illustrating yetfurther aspects of the present invention; and

[0019]FIG. 7 is still another sole view like each of FIGS. 5 and 6, andillustrating even further aspects of the present invention.

DETAILED DESCRIPTION

[0020] Referring to FIG. 6, consider an imaginary horizontal plane(parallel to the ground plane) that is orthogonal to the planecontaining the face centerline, and which contains a point X which issubstantially on this centerline plane. The intersection of such animaginary plane with the sole surface of a club head, designated Area 2,is a small area called the lowest point area LPA. For a golf clubinitially to contact the ground at point X rather than at a point LP onthe downswing, any portion of the sole of the club head lower than pointX should be removed, such that point X and no point lower than point Xis the initial contact point of the club head with the ground duringball striking. Removal of such lower points may result in a lowest pointarea like LPA Area 2. While, as initially identified above, LPA Area 2is planar, it need not necessarily be planar. And, while it isillustrated as elliptical or circular, it need not have that perimetershape. And, it could be simply two or more points, a line or othersurface area. Once any excess material has been removed in forming LPAArea 2, as generally described above, curvature, such as curvaturesimilar to the sole radius, may be imparted to that area as desired, solong as no point in the LPA is lower than point X which remains theinitial contact point with the ground during ball striking with a clubhaving such a club head.

[0021]FIG. 7 illustrates the sole of the club head in address positionwith the toe slightly elevated. An imaginary horizontal plane that isparallel to the ground plane and which contains the intersection pointbetween the sole surface (Area 1) and the vertical line passing throughthe center of gravity, intersects the sole surface forming an Area 3. Tominimize face to back offset with respect to the center of gravity ofthe club head, of the static point of contact SCP, and to prevent theclub head from undesirably opening or closing at address, any portion ofthe sole of the club head lower than the static contact point SCP whenthe club head is in an address position should be removed. Such materialis preferably removed so that the point of intersection between asubstantially vertical line passing through the center of gravity andthe sole surface is the static contact point SCP between the club headand the ground plane when the club is in an address position. Removal ofsuch lower material may result in a static contact surface area SCA likeArea 3. If SCA Area 3 is removed as described above, curvature also maybe imparted thereto as desired, so long as the point of intersectionbetween the vertical line passing through the center of gravity and thesole surface remains the lowest static contact point SCP when the clubhead is in an address position. While the static contact area SCA isillustrated as elliptical in shape, it need not have that perimetershape, and it could be simply two or more points, a line or othersurface.

[0022] Thus, as indicated in FIGS. 6 and 7, LPA Area 2 and SCA Area 3will have bounce angles different from those of the sole surface Area 1.Those skilled in the art will appreciate that the bounce angle specifiedfor Area 2 may be between zero and about 20 degrees. The bounce angle ofeach of LPA Area 2 and SCA Area 3 may vary with respect to the bounceangle specified for Area 1, by up to about 5 degrees. It will also beappreciated that the present invention may be facilitated by modifyingsole width, sole radius, and/or sole camber in addition to or in lieu ofmodifying bounce angle. And, the specific topographies of each of LPAArea 2 and SCA Area 3 may be achieved by using a number of differentmanufacturing methods, including casting, machining, grinding,polishing, or any other method of appropriately shaping those specificareas of a club head.

What is claimed is:
 1. An iron-type golf club head comprising a sole, acenter of gravity CG, and a static contact point SCP on said sole, saidSCP being substantially vertically below the CG when said club head isin an address position, and said sole has no points lower than said SCPwhen said club head is in the address position.
 2. The golf club head ofclaim 1, wherein the SCP and at least one other point substantiallyvertically below the CG define a static contact line SCL.
 3. The golfclub head of claim 1, wherein the SCP and at least two other pointssubstantially vertically below the CG define a static contact surfacearea SCA.
 4. The golf club head of claim 3, wherein the static contactsurface area SCA is planar.
 5. The golf club head of claim 3, whereinthe static contact surface area SCA is non-planar.
 6. An iron-type golfclub head, comprising a sole, a center of gravity CG, and having acenterline plane orthogonal to the plane of the club face and containingthe centerline of the club face, with the center of gravity lying insaid centerline plane and the lowest point LP on said sole also lyingsubstantially in said centerline plane when the centerline plane issubstantially vertical.
 7. The golf club head of claim 6, wherein thesole additionally comprises a lowest point surface area LPA which iscomprised of points substantially vertically below the center of gravitywhen the centerline plane is vertical, and no points on the sole arelower than said LP when the centerline plane is vertical.
 8. The golfclub head of claim 7, wherein the lowest point surface area LPA isplanar.
 9. The golf club head of claim 7, wherein the lowest pointsurface area LPA is non-planar.
 10. The iron-type golf club head ofclaim 1, additionally having a centerline plane orthogonal to the planeof the club face and containing the centerline of the club face, withthe center of gravity lying in said centerline plane and the lowestpoint LP on said sole also lying substantially in said centerline planewhen the centerline plane is substantially vertical.
 11. The golf clubhead of claim 10, wherein the SCP and at least one other pointsubstantially vertically below the CG define a static contact line SCL.12. The golf club head of claim 10, wherein the SCP and at least twoother points substantially vertically below the CG define a staticcontact surface area SCA.
 13. The golf club head of claim 12, whereinthe static contact surface area SCA is planar.
 14. The golf club head ofclaim 12, wherein the static contact surface are SCA is non-planar. 15.The golf club head of claim 10, wherein the sole additionally comprisesa lowest point surface area LPA which is comprised of pointssubstantially vertically below the center of gravity when the centerlineplane is vertical, and no points on the sole are lower than said LP whenthe centerline plane is vertical.
 16. The golf club head of claim 15,wherein the lowest point surface area LPA is planar.
 17. The golf clubhead of claim 15, wherein the lowest point surface area LPA isnon-planar.